The present invention concerns a safety device for grounding high voltage circuits which are enclosed within pressurized containers.
According to certain military standards for electronic equipment, a safety device is required in all equipment operating above 70 volts whereby circuits can be grounded or discharged in case of failure and repairs. A similar requirement also exists for commercial high voltage equipment. On ground based stationary equipment, this requirement is readily satisfied by conventional grounding rods. On airborne and on some mobile high voltage equipments however, weight and space limitations necessitate enclosure of circuits in sealed containers or tanks which are pressurized with a gas, such as sulphur hexafluoride. The circuits therefore become inaccessible for discharging by conventional means.
In the event that bleeder networks have failed, removing external interconnecting cables in order to gain access to the circuits can expose the operator to high and dangerous voltage unless special precautions have been taken to discharge the high voltages to protect the personnel. The then exposed terminals cannot readily be used for grounding purposes, however, since any procedure that may generate an arc is prohibited in an aircraft or other environment where gasoline fumes may be present. Therefore, a discharge device is needed that performs the grounding within the sealed environment. When in the open position, the device must be capable of safely withstanding the system operating voltage which in a typical system, approximates 85000 volts.
Because of necessary dense packaging of these electronic equipments within the tanks, and because of the desirability of uniformity between tanks, the safety grounding device cannot be installed within the circuitry proper.